Injection equipment

Abstract: Injection equipment for the supply of gas and/or particulate material in the form of powder, granules, chips or similar to a liquid, for example metal melt, comprising a rotation body (1) which is designed to be lowered down into the liquid and which is mounted on and driven via a shaft (2) of a drive unit (4,7). The material and/or gas is supplied to the liquid through the rotor via a coaxial bore in the shaft. The special feature of this equipment is that the rotation body has a cone-like or funnel-like design and is generally completely open at the bottom.

Description: The present invention concerns injection equipment for the supply of gas and/or particulate material in the form of powder, granules, chips or similar to a liquid, for example metal melt, comprising a rotation body which is designed to be lowered down into the liquid and which is mounted on and driven via a shaft of a drive unit. Previous equipment and methods are known for processing and adding particulate material to a liquid as stated above. Thus, EP-A-151434 concerns a rotor for processing and adding material to a liquid, whereby the rotor comprises a rotationally symmetrical hollow body and whereby the material is added to the liquid via a rotating tube or a bore of the rotor shaft and onwards out through a hole in the side of the hollow body together with the liquid which, on account of centripetal force, is sucked in through an opening in the base and circulated through the body. Even if this rotor in itself causes the material to be well mixed in the melt, over time the material will build up inside the tube and rotor, especially where large particles are involved, and eventually block it up completely. Similar equipment is disclosed in EP-A-396267 or in EP-A-495581. DE-A-2622236 relates to an equipment for the supply of material to a metal melt comprising a rotor shaped as a cone, and where material is supplied to the melt through a bore in the rotor shaft. This equipment has no stationary pipe provided in the bore of the shaft, but a lower part of a material holding container is protruding shortly into the upper part of the bore. Usually, cone-shaped bottom of the rotor serres to avoid clogging as in US-A-4004919 or in EP-A-395138. Furthermore, EP-A-0065854 describes a procedure for removing alkaline and earth-alkaline metals from aluminium melts whereby aluminium fluoride is introduced in powder form into an eddy produced in the melt. Processing takes place in a cylindrical container with the ability to hold 3-5 tonnes of aluminium melt. This known method requires a lot of agitation of the melt to obtain the desired effect. However, such powerful agitation is not desirable as it causes air to be pumped into the melt. Furthermore, the quantity of aluminium fluoride which is required to process each tonne of melt is relatively high. Other generally known methods (cf., for example, Norwegian patent application no. 881370 corresponding to EP-A-285566) involve adding the powder to a melt by means of a carrier gas through one or more lances. The disadvantages of using lances are that the consumption of gas is high and the efficiency is low. Even if the efficiency can be increased somewhat by also using an agitation device, the consumption of gas is equally high and the particles continue to be too poorly mixed in. With the present invention, injection equipment has been invented for adding particulate material to a liquid, for example metal melt, which is considerably more efficient than known solutions and which has considerably wider application in that it can be used not only for adding powder such as aluminium fluoride or magnesium fluoride in connection with purifying aluminium melts, but also for adding larger particles such as granules, needles, crushed slag particles or chips in connection with alloying up or remelting. Furthermore, the invention involves little agitation but nevertheless rapid mixture and high utilisation (low consumption) of the additives, for example in connection with melt purification or other liquid processing. Furthermore, the consumption of any gas can be controlled and utilised fully without loss to the environment. The invention is characterized by the features as defined in the attached claim 1. The present invention will be described in the following in more detail by means of examples and with reference to the enclosed drawings where : Fig. 1 shows a schematic diagram of injection equipment in accordance with the present invention and Fig. 2 shows alternative design forms of the rotation body shown in Fig. 1. The injection equipment 5 in accordance with the present invention as shown in Fig. 1 comprises a cone-shaped or funnel-like rotation body 1 which is screwed in place or fastened in another way (not shown in detail) to a shaft 2. The shaft with the rotation body is rotated by means of a drive unit 4 via a belt transmission 7 or similar. In the preferred example shown here, the material is supplied by means of gas (pneumatically) from a container 8 or similar and via a stationary tube 3 which passes through a coaxial bore in a shaft 2. The gas, which is supplied through a supply line 9 and takes the material with it through tube 3, can be returned completely or in part and be reused by passing it back via the space 10 between the pipe and the shaft and out through a pipe connection 11. The quantity of gas which is returned can be adjusted by means of valve 12 on the pipe connection 11. Thus the level of liquid within the cone can be adjusted from a level at which the liquid is at the lower end of the cone to a level at which it is right up by the outlet of the supply tube 3. A surplus of gas may be supplied so that the rotor can also be used for melt purification, for example. In such case the gas will flow out through the downward-facing opening in the cone and, because of the rotation, the gas is finely distributed in the liquid. Preliminary tests have shown that, used for liquid purification, it is at least as efficient as existing rotor solutions. Used for the purpose of adding material to a liquid, the present invention functions in the way described in the above: the material is fed through a shaft via tube 3 to the internal cavity in the rotating cone 1 where it is mixed with the liquid. The cavity or gas pocket is formed as stated above on account of the gas supply and under the cavity in the cone a uniform liquid surface is created which is continually renewed on account of the centrifugal forces which the rotating cone imparts to the liquid. Also, the gas which is located within the cavity in the cone will, as stated, be caused to rotate and when the material, in the form of particles, arrives in the cavity, the particles will partly fall down and be mixed with the liquid directly and partly, on account of the centrifugal force, be slung outwards and downwards and fed along the conical wall and then mixed with the liquid. In this connection, it should be noted that the angle formed by the wall of the cone with the vertical axis must be sufficiently large such that the particles do not stick to the wall, but "skid" along it outwards and downwards. If the level of liquid inside the cavity is above the lower edge, i.e. a little way up in the cone as shown on the drawing, the particles will, when they have come down into the liquid, be fed further outwards and downwards along the wall of the cone by means of the liquid. By raising the level of the liquid inside during operation, the liquid can be made to flow along the internal wall of the cone and thus ensure that any material which has stuck to the wall is removed. An increase in the level of the liquid inside the rotor will otherwise increase the agitation power of the rotor. Using an internal stationary tube, however, avoids material being deposited inside the tube (no centrifugal forces which cause deposits when the pipe does not rotate). Furthermore, regarding the design of the rotor, the expression "cone" is not restricted to the example shown in Fig. 1, but can cover solutions where the cone is partly spherical with a convex or concave wall surface or has a larger diameter with an upper horizontal wall part 14 as shown in Figs. 2a - 2d. Moreover, Fig. 2d shows an example of a rotor which is provided with recesses or milled tracks 13 to increase the agitation power and to improve the spread or distribution of the material in the liquid. Instead of recesses, "nipples" can also be used or blade-like elevations etc.

Claims: Injection equipment for the supply of gas and/or particulate material in the form of powder, granules, needles or similar to a liquid, for example metal melt, comprising a rotation body (1) which is designed to be lowered down into the liquid and which is mounted on and driven via a shaft (2) of a drive unit (4,7), disposing means to supply the material to the liquid through the rotation body (1) via a tube (3) passing coaxially through a bore in the shaft (2), and where the tube (3), stretching through the whole length of the bore, is stationary and is arranged with a clearance in relation to the bore in the shaft (2) so that an annulus (10) is formed between them, said annulus (10) communicating with a pipe connection (11) and that the rotation body (1) has a shape of a cone or a funnel and being completely open at the bottom, characterised in that said pipe connection is further connected to gas exhaust means through a valve (12) whereby the liquid level within the rotation body and return of gas from the rotation body can be controlled.

Inventors: PEDERSEN TERJE, VENAS KARL, PEDERSEN, TERJE, VENAS, KARL
Applicants: NORSK HYDRO AS, NORSK HYDRO ASA
Application year: 1994
Main classification: C22B9
IPC codes: F04D1, B01J4, B01F5, F27D3, C22B9, C22B21, C21C7, B67D7